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If you just got a new puppy, a whole journey is ahead! A puppy will bring a lot of joy to your home. He will quickly grow into an adult dog, meaning rapid changes will happen. However, no need to worry. We will explain the various stages of puppy development and what you should do at each one. We are sure that with this information, he will soon become a beloved family member.

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Your puppy will answer to his new home according to his temperament and characteristics common to his breed. Pups are often initially scared and anxious. 

Other pups are thrilled with their new home. Your new puppy may start running around, jumping on you, or licking you with great excitement. This is normal, but you need to be cautious about this behavior to ensure it does not trigger aggression in the future. 

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Take a look at what you can expect in the various stages your puppy will go through. It is essential to understand in detail what can happen in this process so that you can help your new little best friend. 

Little puppy on his owner's lap.

Phase 1: Birth to 3 Weeks

Your puppy should not be away from his mother throughout this time since he will depend on her, especially for regular feedings. In this early stage, puppies eat every 3-4 hours.

Mom dog who just had puppies.

During pregnancy and nursing the puppies, the puppy's mother's food must be rich in protein and calories. It must also include DHA and EPA, essential fatty acids for your puppy's brain development. You can choose foods intended for older dogs as they often have servings of these acids. 

If you take care of a puppy apart from his mother during this stage, you must bottle feed a puppy milk replacer. You should consult a veterinarian to understand the best puppy milk replacer for your dog.

Puppy taking a baby bottle.

What can you expect?

You can expect your puppy to sleep a lot in these first few weeks! The puppy's senses are not developed yet, so your puppy can't hear, smell or see. 

During this period, fur will start to grow on your puppy. Puppies may also start trying to stand or crawl as their muscles and awareness develop. When they reach approximately three weeks old, they will most likely open their eyes and take their first steps. 

Although your puppy's life is mostly about eating and sleeping during these first three weeks, we promise this calmness won’t last long. Enjoy it while it lasts.

Five little puppies sleeping.

What should you do?

  • Minimize contact with other dogs and people as much as possible since puppies are highly vulnerable to disease during this initial stage.
  • Feed the puppy’s mother appropriately.
  • Keep the pup with his mother until he is weaned, if possible.
  • If you are bottle-feeding a puppy milk replacer, use the one recommended by your veterinarian.  

Phase 2: 3 to 4 Weeks

What can you expect?

During this week, many things take place! Your puppy’s eyes will open, he will start interacting with others, and his other senses will develop. He will begin to walk and maybe even wag his tail or bark. You will definitely hear lots of cute whines as he finds his voice. He will also start to eliminate without his mother's stimulation, and his tiny teeth will begin to show up. 

Weaning starts this week too. Combine puppy milk replacer with puppy food to progressively shift your puppy’s diet to solid food. Then, it would be best to give this mixture to your puppy between nursing sessions. Add more and more dog food to the mix until it's just solid food. To better understand how to wean puppies, check out this guide. 

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In this period, your puppy will achieve some independence. He will try to explore the world around him, playing with his siblings or showing interest in humans. This is when puppies connect with people, so feel free to hold and pet your pup gently.

What should you do?

  • Start to wean your puppy gradually by introducing a small quantity of solid food into his diet.
  • Hold and pet your pup a lot! This is vital for your puppy to learn to interact with humans.
  • Maintain your puppy separate from other dogs since he is still susceptible to illness.
Woman holding four puppies in her arms.

Phase 3: 1 to 3 months

Around this time, puppies are prepared to leave their moms. They are sufficiently mature to adapt to a different environment. They are weaned and safe from catching diseases since the first vaccinations against illnesses are taken at approximately six weeks. Thus, this is the stage when most people bring home their puppies. If you are adopting a puppy six weeks old or older, get his vaccination records and check with your veterinarian that they are current.

You should start obedience and potty training your pup during this stage. However, remember that his elimination muscles are not fully developed, so you must take him outside each hour or two.

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What can you expect?

During these months, your pup will be extra curious about the world around him. Puppies pass through the socialization period between 5 and 16 weeks of age. During this period, they should have as many diverse experiences as possible so they won't become frightened of different things later in their lives. Therefore, try introducing them to people, children, and animals of all shapes and sizes and new experiences, such as car rides or doorbells. 

Happy dog at the car window.

However, you will need to be careful! Around 6 and 8 weeks of age, there is a fear period. At this time, your puppy will be fearful and easily impressionable. You must avoid potentially scary or painful experiences, which can lead to lifelong phobias. 

One of the most important aspects is that this is when your pup creates strong attachments with you and others around him. You are forming a solid lifelong relationship!

What should you do?

  • Make sure your puppy’s vaccines are up to date.
  • Introduce your puppy to many new people, animals, and experiences. 
  • Avoid experiences or interactions that can be scary for your puppy during his fear period between weeks 6 and 8.
  • Start potty and obedience training, but remember that your puppy is still incapable of perfection. This will be a gradual process, so have lots of patience and start with the basics. Check out some easy-to-understand obedience training methods.

    A dog obeying its owner/trainer's command.

Phase 4: 3 to 8 months

What can you expect?

Your puppy will start to teethe and need to chew on something. To redirect him from your shoes and furniture, make sure you provide him with some chew toys. They are great for the puppy to cut teeth on.

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You may also expect your puppy's body to grow a lot during this puppy stage! His weight will change quickly during these months, mainly if he is a large-breed dog. His cartilage will harden, and his bone will begin to fuse. This will make your pup more vulnerable to injuries, so you should watch him closely and leave him in a safe place when you are not paying attention, such as a dog crate or pen. The positive aspect is that this leads to that clumsy and goofy pup play that warms our hearts. 

During this period, you will need to look into spaying or neutering. Female dogs usually go through heat between 4 and 6 months, while male dogs can generate sperm and mate with a female between 6 and 9 months. If you have a male puppy, he might even begin “marking” his territory with his urine, so be ready for that!

Two little pomeranian dogs.

Between 3 to 8 months, your pup will start making independent decisions. This is the time when his personality will emerge. In fact, you may often spot him confused about following some order you gave him. You must be patient and understand that this is a natural part of his development. Also, remember that it is good that he achieved a stage where he is using decision-making skills. 

Sometimes, another fear period occurs from 6 to 8 months old. This may only be the case with some puppies but pay attention anyway. This will not be as exacerbated as the first one. However, it would be best to remain cautious about stressful circumstances. Avoid potentially frightening or traumatic situations to prevent your dog from developing phobias or negative associations.

A puppy chewing his toy.

What should you do?

  • Give your puppy healthy and appropriate toys for his size and age. These toys help puppies deal with the discomfort of growing adult teeth.
  • Puppies must finish their vaccinations by around 16 weeks of age. At this age, they should also start receiving preventatives for heartworm and flea and tick prevention. Talk to your vet to ensure this happens. 
  • Use a dog crate or pen when you can’t supervise your puppy to keep him away from injuries.
  • Discuss with your vet spaying or neutering.
  • This might be an excellent moment to enroll in training classes. You will learn how to train your pup correctly, and he will socialize with other dogs and people. 
  • Remember to introduce your puppy to different people, places, situations, and animals. This is crucial for his development, confidence, and safety. 
A puppy chewing his toy.

Phase 5: 8 to 12 months

What can you expect?

For some small-breed dogs, like Chihuahuas, this stage marks the end of their puppyhood. This is because they stop developing when they are one year old. However, large-breed dogs, such as Golden Retrievers, are considered puppies until they are about 18 months old. If you have a giant-breed dog, like a Mastiff, be aware that he can be considered a puppy for up to 24 months.

This “puppy status” has implications for your dog's diet. Every dog must eat puppy food until 10 to 12 months. However, large-breed dogs may need to maintain this diet until 18 or 24 months of age. This guarantees they get all the nutrients needed for proper growth and development. You should also ensure that they eat food designed for large breeds, which are lower in calories but higher in glucosamine and chondroitin. These two compounds are essential for your pup's healthy growth. 

Consult your veterinarian to understand when the shift to adult dog food must be made.

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What can you expect?

From 8 to 12 months of age, your puppy will keep his curiosity and jokiness. He may continue to test your limits with some independent decision-making. Since he is now a teenager, he will try to establish himself in the pack and challenge the people and pets around him. You can expect certain misbehavior and disobedience, especially now that he is becoming sexually mature. Remember that this is part of the process, and keep training him. 

At this age, puppies need a lot of stimulation and activity, so give your pup several opportunities to play and exercise. Give him the freedom to explore without forgetting the importance of obedience. Dog obedience training is incredibly beneficial for you and your dog, particularly in the first three years of his life.

 Happy dog running on the grass with his ball in his mouth.

What should you do?

  • Discuss with your vet the appropriate moment to shift your dog’s diet to adult food.
  • Take obedience classes or be the instructor yourself to stimulate your pup's mind.

Phase 5: 12 to 24 months

What can you expect?

At this point, you can expect your puppy's body to be more like an adult dog's body. However, until your pup is fully grown, he is quite susceptible to injury, and you need to avoid all sorts of repetitive training.

The majority of dogs are emotionally mature at this stage. This means they have reached the personality and temperament they will maintain throughout their lives. However, this also means that some behavioral issues you overlooked when your pup was younger may need to be addressed now. These are previously seemingly minor issues, such as some sensitivity to noise, that could lead to more significant issues in the future. 

If you have any concerns, see a veterinary behaviorist.

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During this age, you can still expect loads of energy from your dog that might last for many more years, depending on his breed.

What should you do?

  • Avoid repetitive training, like running or walking for a long time, until you are sure your puppy is fully grown.
  • Talk with a veterinary behaviorist if your dog has any anxiety or phobias.

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The Bottom Line

Congratulations! If your puppy has gone through all these stages, he's already a grown-up!

Over the past two years, you have given your puppy a safe environment and prepared him for adulthood. Now you know him like no one else, and you have created a special bond with him that will last forever. 

Dogs always remain cute and playful throughout their lives but never stop requiring attention. So, keep giving your pup lots of affection and love. 

A dog owner hugging his dog.

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